1. Field of the Invention
The invention relates to polycarbonate resins and more particularly to polycarbonate resins with a polymer chain terminated by a hydroxyl group, their method of preparation and use.
2. Brief Description of the Prior Art
Although not prior art to the present invention, hydroxyl polycarbonate resins and their method of preparation are described in the now copending U.S. patent application Ser. No. 939,391 filed on Dec. 8, 1986, now U.S. Pat. No. 4,732,934, by Pyles, Longely and Hathaway. The method of preparation entails the use of a mono protected bishydroxyl compound such as shown in the formula: ##STR2## wherein R' represents alkylene or arylene, as the chain terminating agent in the preparation of the resins, followed by removal of the protecting group to generate a hydroxyl-terminated polycarbonate resin.
These hydroxy terminated resins were subsequently converted via reaction at the hydroxy group to reactive end group resins useful in polymer blend and copolymer preparation.
Other hydroxyl-terminated polycarbonates were also known prior to the present invention. However, hydroxyl group terminated polycarbonate resins are generally difficult to prepare, especially when made directly in the convenient and well known interfacial polymerization reaction. The difficulty arises because conventionally in this technique it is most convenient to react an equivalent excess of carbonyl halide with a bisphenol and a mono-functional chain terminating agent. However, to produce hydroxyl terminated resin directly in this process, the chain terminating agent would be deleted and slightly less than an equivalent of carbonyl halide would be needed. Because of difficulties of controlling carbonyl halide addition rates and of controlling its losses to side reactions and volatilization, this leads to difficulties in controlling the hydroxyl end group levels and the resin molecular weight.
The method of the present invention permits one to prepare polycarbonate resins having hydroxyl terminal groups, from an interfacial polymerization. The polymers obtained have end group structures which are useful to prepare polycarbonate copolymers with properties useful in thermoplastically molded articles.